A couple of days ago, my 10-year-old nephew's attention was caught by a trailer for a Dispatches programme going out on Channel 4 tomorrow night. The trailer was only a few seconds long, but it left him feeling confused and upset. He went to find my sister-in-law to ask her if he'd understood properly what he'd heard. "Mum, I've just heard there's a programme about how dyslexia doesn't exist," he said. "That's not true, is it?"

My sister-in-law felt her hackles rise, as she's felt them rise often over the six or seven years she's battled to get her son a statement of special needs for his dyslexia. "Every day of his life, my son has to go to school and see other children who are no brighter than him do better than him," she says. "And every day I have to tell him why that is. 'You're not less bright than them,' I tell him. 'You're dyslexic.' "

My sister-in-law hasn't yet joined the ranks of angry parents sending hate emails to Professor Julian Elliott of Durham University, the academic at the centre of the storm that has broken over the existence, or otherwise, of dyslexia, but if she had his email address I suspect she might very well do so. For parents like her, who have spent years trying to get their children's reading, language and writing difficulties dealt with properly in the classroom, the moment the official label of "dyslexia" arrives is a moment of triumph. Doors are opened, classroom assistants are allocated, special help is given. And, best of all, the dyslexia test incorporates an IQ test, to prove, to any doubters out there, that your child isn't simply thick.

Elliott is well aware of the anger and emotion he's going to stir among viewers tomorrow night, and has already stirred up with a newspaper article at the weekend: after all, he says, his work as an educational psychologist dealing with children with reading difficulties has put him in close proximity with these very families for the past 30 years. But, despite all his experience, he doesn't believe he could find any difference between a child labelled "dyslexic" and a child labelled "a poor reader". In other words, he doesn't believe that, amidst the broader group of struggling-to-read children, there is a special group of kids with a different IQ who need special intervention to help them overcome their reading problem. What's more, he says, there are simply too many so-called dyslexic children to make the term meaningful: once you get such a high number of children as there are today labelled with a condition such as dyslexia (that's around 375,000 in this country), you've simply got to question whether there's any real basis to the label at all.

So far, so nasty: what Elliott's arguments sound like is a big hammer to bash all those middle-class parents who've decided that their struggling-to-read child can't be just, well, struggling to read. The British Dyslexia Association has described his views as "very damaging and insulting to people who are trying to overcome their dyslexia".

Elliott, however, says he has been misunderstood: "I can understand parents wanting to get this label, because there's a human need for labels. But what parents believe is that the label will lead to an intervention, in much the same way that a diagnosis of a broken arm leads to effective treatment. And what I'd argue is that the intervention they receive when their child is labelled dyslexic isn't effective - and furthermore, it's very expensive and time-consuming, and it diverts resources away from what could be being done better to help all children with reading problems."

At the root of this, says Elliott, is the widespread misconception that an inability to read and write and use language effectively is linked with IQ. "In fact, reading isn't something that requires a high level of intelligence," he says. "Amongst children who struggle to read, you find some with a high IQ, some in the middle and some with a low IQ." The real tragedy of that misconception lies in the fact that children who are poor readers are too often assumed to be less capable: they are put into the lower teaching groups, given easier work at school, and are not intellectually challenged as they should be. And what that means, in turn, is that they not only underachieve, they also become disaffected by the education process and become unenthusiastic about learning.

In one sense it's to overcome that danger that so many parents seek out the dyslexia label, which brings with it dividends of extra help and encouragement in the classroom. But, says Elliott, their attempt to put a sticking plaster over their own kid's wound has led to resources being diverted away from children for whom a more comprehensive programme of intervention might be far better deployed. "There's an element of unfairness in all this, because there's clearly a group of clued-up parents who are able to take a certain route, get their child labelled dyslexic and then get more help than other children struggling to read," he says. By the same token, there's another group of not-so-well-informed parents whose kids are not getting the help that would make a difference - and whose long-term prospects suffer colossal damage as a result.

And crucially, Elliott goes on, there's now evidence from research at York University that shows - contrary to what you might have expected - that children with a low IQ can be helped just as much with reading problems as children with a high IQ, providing it's the right reading programme and providing it's implemented in the right way. What you might have expected is that children with a low IQ wouldn't progress as quickly as children with a high IQ: but what these studies in York have found, he says, is that they do.

And what that means is that it's misguided as well as unfair for resources to be concentrated amongst just one group of poor readers rather than across the group as a whole. According to academics interviewed in the Dispatches programme, there is now an overwhelming body of evidence to prove that it's intervention as early as possible in life that pays off: in particular, a programme pioneered in Cumbria has produced extraordinarily successful results, raising the reading age of children by eight or nine months after just a 12-week intensive course - a result that is, apparently, seven or eight times better than other conventional programmes for dyslexics. The bottom line is obvious: resources should be taken away from the expensive and time-consuming process of identifying dyslexics, often when they're well into primary or even secondary school, and sunk instead into a top-notch early intervention catch-all scheme that targets all poor readers as early as possible, and deals with them efficiently at the point of diagnosis and not years down the line, and only then if their parents manage to get a statement of special needs.

At the moment, millions of pounds alone are spent on the process of merely identifying children with dyslexia. There's no uniform test, and different psychologists have different ideas about which things to look at: but Elliott's view is that they're all a waste of time and money. "Some tests look at memory, some at sounds and words, some at visual processing," says Elliott. "The traditional route was to identify a child whose IQ was high, but whose reading level was low: that test is still being used in some places, although you could ask why look at a child's IQ when deciding if they need special reading help? But the bottom line is that experts can't agree precisely what set of problems make up the condition they call dyslexia: and if you can't agree on what a condition is, how on earth can you test for it?" Or to put it another way, as they do in the Dispatches programme: either every child with poor reading ability is dyslexic, or none of them is.

Another part of the jigsaw is new research that shows that reading difficulties may be due to some not-yet-understood brain malfunction: what experts believe is there's some area of the brain that distinguishes the tiniest differences between sounds that doesn't work properly in some children, and this affects their reading. The cause could be genetic - half of all reading problems are inherited - but environment is important too, and early exposure to talking, songs and nursery rhymes could all help reduce the impact of this problem if it is present, while a lack of early interaction could lead to damage even where there isn't an inherited disorder.

All of which leads Elliott to the conclusion he believes hasn't yet been properly understood, which is that all kids - including those who will later be labelled as dyslexics - would be helped, and hugely, by an early intervention programme such as that used in Cumbria (one other authority, North Yorkshire, is about to introduce it too, but others are lagging behind). The programme targets, initially, all children to help reinforce the importance of distinguishing every sound: it then picks out those having difficulties, and gives them extra help. The results, according to Dispatches, is stunning. Parents shouldn't be resistant to his claims, he says: what he and his colleagues are suggesting is a way of identifying all children with a problem, and a lot earlier on.

It all sounds very convincing, but I suspect that, when the telly goes off at my sister-in-law's house tomorrow evening, there will still be upset and confusion. The problem is that parents such as my sister-in-law are forever hearing that the truth about dyslexia is this, or this, or that: they're all researched out. And even if they did buy into Elliott's thesis, early intervention programmes aren't going to be any good to them now. For families like them, giving up the dyslexia label they have fought tooth and nail for isn't going to be easy. How do you tell kids such as my nephew that the condition that has come to define their lives may actually be just a fairytale?